1. Field of the Invention
The invention relates to a drive arrangement for motorized actuation of a functional element in a motor vehicle with at least one drive, the drive having a drive motor and a spindle-spindle nut gear connected downstream of the drive motor for producing linear drive movements, the spindle-spindle nut gear having a spindle with an outside thread and a spindle nut with an inside thread, and the linear drive motion being moving the spindle nut parallel to the spindle axis.
2. Description of Related Art
Within the framework of enhancing the ease of operation in motor vehicles, drive arrangements of the type under consideration are becoming more and more important. The functional elements which can be moved by a motor here are, for example, hatches, especially rear hatches, rear covers, side doors or lifting roofs, vehicle seats or the like. In addition to high reliability and low costs, the compactness of such a drive arrangement plays an important part.
The known drive arrangement underlying the invention (U.S. Pat. No. 6,516,567) has a drive arrangement for motorized actuation of the rear hatch of a motor vehicle with two drives which act on the two side edges of the rear hatch by drive engineering. The drives each have a drive motor and a spindle-spindle nut gear connected downstream of the drive motor. The spindle-spindle nut gear, as is conventional, has a spindle with an outside thread which runs in the inside thread of a spindle nut. Driving the spindle allows the spindle-spindle nut gear to be moved between a retracted and an extended state. A linear drive motion, specifically motion of the spindle nut, parallel to the spindle axis, can thus be comparatively easily implemented.
The disadvantage in the known drive arrangement is that the spindle-spindle nut gear has a considerable length in the retracted state. This is due to the fact that the length of the spindle must correspond at least to the length of the desired feed path. This costs installation space in the interior of the vehicle which is fundamentally dimensioned to be tight. The large extension of the drive arrangement is also a problem in terms of aesthetics.
Furthermore, it must be considered that each rear hatch of a motor vehicle has a quite defined closing and opening characteristic. This means that the expenditure of force necessary to open or close the hatch changes when viewed over the entire closing and opening motion. For example, it can be that, to open the rear hatch of a motor vehicle, initially, an especially high force is necessary until gas pressure dampers which may be present support the opening motion. However, it can also be that these gas pressure dampers are not provided, so that the expenditure of force necessary for the opening motion is maximum when the hatch is almost completely opened. The design of the spindle-spindle nut gear, on the one hand, and the drive motor, on the other hand, therefore, constitutes a compromise in the known drive arrangement, in any case. This compromise leads to high costs since the drive motor is over-dimensioned for a considerable part of the positioning motion of the rear hatch.